Do You Have Chimpanzee Feet?

8% of people have midfoot flexion similar to other primates' feet.

About 8% of people tested by Boston University researchers had midfoot flexibility of the sort that apes use to climb trees, according to a study published in the American Journal of Physical Anthropolgy.

As New Scientist reports, the researchers had people walk around the Boston Museum of Science barefoot while the researchers videotaped them and measured their plantar pressure. Of the 398 people studied, 32 had "elevated lateral midfoot pressures and even exhibit midfoot dorsiflexion characteristic of a midtarsal break," the researchers wrote. In other words, feet that bend in the middle in ways similar to the feet of chimpanzees, gorillas and other great apes.

One of the researchers, Jeremy DeSilva, told New Scientist that the people with the midfoot-flexible feet were unaware of this characteristic, and that their walking gait was similar to that of the vast majority with more rigid midfeet.

One theory for why humans have much more rigid midfeet than other primates is that more rigidity better allows the foot to act as a lever during the bipedal gaits of walking and running. In the Boston University study, the people with more flexible midfeet had, on average, flatter feet and showed greater pronation, or rolling in of the foot after landing, than others.

Despite his obervation that there was no difference in gait between those with apelike feet and those with more rigid feet, DeSilva said that he thinks people with apelike feet are less efficient walkers (and presumably, runners).

DeSilva told New Scientist he thinks the trait has reappeared among humans as walking and running have become increasingly inconsequential in daily life, as opposed to the more flexible feet being an evolutionary vestige.

"My guess is that we are getting more variation than ever before, perhaps because shoes have impacted foot anatomy," DeSilva said.